ALBANY — Terrell Thomas says he feels like a rookie again, anticipating not just the first practice of training camp, but his first practice since a devastating knee injury last preseason kept the potential Pro Bowl cornerback from being part of the Giants Super Bowl team.

It was about 90 minutes before the 2012 Giants took the field for their first practice of training camp yesterday. During all the months and weeks of rehabbing his surgically repaired anterior cruciate ligament in his right knee, Thomas had been pointing to this day, when he could get back on the field, practice at full speed and feel like a football player again.

“It’s finally here,” he said during his lunch break. “I’m excited to get out there and see the results of all the hard work I put in, get out there and be with my teammates and get back to playing football.”

But less than 15 minutes into the practice, Thomas was on the sidelines again with his helmet in his hand and looking dejected. Afterward, he tweeted what happened.

“I’m OK back locked up on me…back to rule #1 #GODSPLAN.”

Giants coach Tom Coughlin used traditional English to report the situation: “His back was tight,” the coach said with a shrug. “His legs were fine.”

It was a discouraging start that will surely test Thomas’ faith and patience. This was supposed to be a new beginning, not a setback.

“No way!” That was the reaction of John Meyer, Thomas’ physical therapist, when he learned of the back trouble.

“He’s been doing way more than what he was going to do in practice,” said Meyer, who supervised Thomas’ rehab program at Conatus Athletics in Los Angeles. “I’ve been having to keep the reins on him. He’s been going crazy. But he’ll get through that. That happens. But it won’t be anything long-standing.”

#GODSPLAN. That’s how Thomas got through a difficult 2011. Drafted in 2008, he was a mainstay of the Giants defense, entering the final season of a contract that meant wealth and security when he became a free agent at the end of the year. But all that changed when he collided with teammate Jason Pierre-Paul late in the first half of a preseason game with the Bears and tore the ACL in his right knee, the same injury he suffered in 2005 at USC.

“It was a shock,” Thomas said. “I instantly knew what everything entailed as far as the rehab ahead and as far as my contract and everything else I faced. It was disheartening. It couldn’t have come at a worse time. But things happen for a reason.”

#GODSPLAN. That’s how he approached his rehab with Meyer, working out and rehabbing twice a day, three thousand miles from his teammates who rallied from a 7-7 record to win six straight games, including the Giants’ second Super Bowl in four years. At first, Thomas stayed in California because he didn’t want to be a “distraction” to his team. But he was on the sidelines for the postseason victories against the Falcons, 49ers and Patriots.

Yes, he got a ring when they were handed out during a ceremony a few days after he signed a four-year ,incentive-laden contract that could be worth $28 million. But he took off the ring in the cab on the way home that day and doesn’t plan to wear it anytime soon.

“I texted some of my teammates and told them, ‘I appreciate what you did for me, but I want to win one playing with you all’ and it starts today,” he said.

Despite what happened yesterday, that goal doesn’t change. In fact, Thomas didn’t even mention his back issues when he texted Meyer late yesterday.

“He’s an extremely hard worker,” Meyer said. “I think he’s going to do great. I don’t think he’s going to have any problems. This won’t be a setback.”